３ INTERNAL CONNECTION
ＭＵＸ-１００ SERVICE MANUAL
３ - ４
３-２ Basic Operation of Each Part
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２
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１
Power ON/OFF operation
Related PCB: MUX POWER PCB
Ⅰ
Power ON operation
ⅰ
When the key switch is set to ON, all of four contacts of the key switch are closed.
It means that all of three contacts of the connector JKEY on MUX POWER PCB are closed.
(Another one more contact of the key switch is used for Power On/Off circuit of DR system.
Refer to 3-2-7.)
ⅱ
The battery voltage 240 VDC is input to PS1 on MUX POWER PCB, and 12V is output.
ⅲ
The latch relay K9 turns ON, and the relay K6 turns ON.
ⅳ
As a result, the power is supplied to each part via the current restraining resistors R1 and R2 (150
Ω
) in
the control unit and the connector JRS.
ⅴ
Because the power is supplied to the DC pack PS1 and PS2 through the connector JDC, 5V, 15V and
24V are output and the control PCBs starts to operate.
ⅵ
After check by the NEXSC (CPU) PCB is completed (in approximately 1 to 2 seconds), the MGRS
signal is sent to the XCONT PCB and the MUX CHARGE-04A PCB to turn ON the relay K4.
As a result, the relay K7 turns ON, the route through the R1 and the R2 in the control unit is
short-circuited, and sufficient load current can flow.
ⅶ
When the MGRS signal is output, the system becomes ready for operation.
(Reference) The ON status of the key switch (the KEYSW signal) is transmitted to the XCONT PCB via
the MUX CHARGE-04A PCB, then it is recognized by CPU as the fact that the KEYSW1
line and the KEWSW2 line are short-circuited.
Ⅱ
Power OFF operation
ⅰ
When the key switch is set to OFF, the relay K7 turns OFF first. Though the input to the PS1 in the DC pack
stops, the output remains for a while. Accordingly, the relay K6 turns OFF after a while. By this operation,
the power supplied through the resistors R1 and R2 remains for a while because excessive load is applied on
contacts if all contacts are opened at the same time.
Ⅲ
Auto power OFF operation
ⅰ
In the power ON status, the CPU outputs the AUTOOFF signal through XCONT and MUX CHARGE-04A
PCBs to set the relay K5 to ON. As a result, the latch relay K9 turns OFF, the relays K6 and K7 turn OFF,
the power supplied to the DC pack stops, then the system stops.
ⅱ
In this status, PS1 on MUX POWER PCB is continuing operation. Accordingly, if the system is left in the
auto power OFF status, the batteries are discharged in a long period due to the fine discharge current.
